Metal (II) phosphate powders, lithium metal phosphate powders for Li-ion battery, and methods for manufacturing the same

ABSTRACT

Metal (II) phosphate powders, lithium metal phosphate powders for a Li-ion battery and methods for manufacturing the same are provided. The lithium metal phosphate powders are represented by the following formula (II):
 
LiFe 1-a M a PO 4   (II)
 
wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5&lt;a≤1, the lithium metal phosphate powders are composed of plural flake powders, and a length of each of the flake powders is ranged from 50 nm to 10 μm.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part (CIP) of U.S. Patentapplication for “Ferrous Phosphate Powders, Lithium Iron PhosphatePowders for Li-Ion Battery, and Methods for Manufacturing the Same”,U.S. application Ser. No. 16/016,968 filed Jun. 25, 2018, and thesubject matter of which is incorporated herein by reference.

U.S. application Ser. No. 16/016,968 filed Jun. 25, 2018 is acontinuation-in-part (CIP) of U.S. application Ser. No. 15/853,579 filedDec. 22, 2017; U.S. application Ser. No. 15/853,579 filed Dec. 22, 2017is a continuation-in-part (CIP) of Ser. No. 14/705,618 filed May 6,2015; U.S. application Ser. No. 14/705,618 filed May 6, 2015 is acontinuation-in-part (CIP) of Ser. No. 14/057,372 filed Oct. 18, 2013;U.S. application Ser. No. 14/057,372 filed Oct. 18, 2013 is acontinuation-in-part (CIP) of U.S. application Ser. No. 13/908,393 filedJun. 3, 2013; and U.S. application Ser. No. 13/908,393 filed Jun. 3,2013 is a continuation-in-part (CIP) of U.S. application Ser. No.13/524,287 filed Jun. 15, 2012, which claims the benefits of the TaiwanPatent Application Serial Number 100121234, filed on Jun. 17, 2011.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to metal (II) phosphate powders, lithiummetal phosphate powders prepared therefrom, and methods formanufacturing the same. More specifically, the present invention relatesto metal (II) phosphate powders for preparing Li-ion batteries havinglarge length to thickness ratio, lithium metal phosphate powdersprepared therefrom, and methods for manufacturing the same.

2. Description of Related Art

As the development of various portable electronic devices continues,more and more attention focuses on the techniques of energy storage, andbatteries are the main power supplies for these portable electronicdevices.

Among commercial batteries, small-sized secondary batteries areespecially the major power supplies for portable electronic devices suchas cell phones and notebooks. In addition, secondary batteries areapplied to not only portable electronic devices, but also electricvehicles. Among the developed secondary batteries, the lithium secondarybatteries (also named as the Li-ion batteries) developed in 1990 are themost popular batteries used nowadays. The cathode material of theinitial lithium secondary batteries is LiCoO₂. LiCoO₂ has the propertiesof high working voltage and stable charging and discharging voltage, sothe secondary batteries which use LiCoO₂ as a cathode material arewidely applied to portable electronic devices. Then, LiFePO₄ with anolivine structure and LiMn₂O₄ with a spinal structure were alsodeveloped as a cathode material for lithium secondary batteries.Compared to LiCoO₂, the safety of the batteries can be improved, thecharge/discharge cycles can be increased, and the cost can be furtherreduced when LiFePO4 or LiMn₂O₄ is used as cathode material of secondarybatteries.

Although the batteries which use LiMn₂O₄ as cathode materials have lowcost and improved safety, the spinal structure of LiMn₂O₄ may collapseduring the deep discharge process, due to Jahn-Teller effect. In thiscase, the cycle performance of the batteries may further be decreased.When LiFePO₄ is used as cathode material of batteries, the batteriesalso have the properties of low cost and improved safety. In addition,the capacity of LiFePO₄ is higher than that of LiMn₂O₄, so the batteriesmade from LiFePO₄ can further be applied to devices which need largecurrent and high power. Furthermore, LiFePO4 is a non-toxic andenvironmentally friendly material, and also has great high temperaturecharacteristics. Hence, LiFePO₄ is considered as an excellent cathodematerial for lithium batteries. Currently, the average discharge voltageof the lithium batteries using LiFePO₄ as a cathode material is 3.2˜3.4V vs. Li⁺/Li.

A conventional structure of the Li-ion batteries comprises: a cathode,an anode, a separator, and a Li-containing electrolyte. The batteriesperform the charge/discharge cycles by the lithium insertion andextraction mechanism, which is represented by the following equations(I) and (II).Charge:LiFePO₄ −x Li⁺ −xe ⁻ →xFePO₄+(1−x)LiFePO₄  (I)Discharge:FePO₄ +x Li⁺ +xe ⁻ →x LiFePO₄+(1−x)FePO₄  (II)

When a charge process of the batteries is performed, Li ions extractfrom the structure of LiFePO₄; and the Li ions insert into the structureof FePO₄ when a discharge process is performed. Hence, thecharge/discharge process of the Li-ion batteries is a two-phase processof LiFePO₄/FePO₄.

Currently, the LiFePO₄ powders are usually prepared by a solid-stateprocess. However, the property of the product is highly related to thethermal-annealing temperature of the solid-state process. When thethermal-annealing temperature is below 700° C., all the raw materialshave to be mixed well. If the raw materials are not mixed well, Fe³⁺impurity phase will be present in the LiFePO₄ powders. Whenthermal-annealing temperature is below 600° C., the average grain sizeof the LiFePO₄ powders will be smaller than 30 μm. However, if thethermal-annealing temperature is increased, the average grain size ofthe LiFePO₄ powders will be larger than 30 μm. When the average grainsize of the LiFePO₄ powders is larger than 30 μm, a grinding process anda sieving process have to be performed to obtain powders with specificgrain size between 1 μm to 10 μm, in order to be used for preparingLi-ion batteries. Hence, in the case that the LiFePO₄ powders areprepared through a solid-state process, the grinding process and thesieving process have to be performed, which may increase the cost of theLi-ion batteries. In addition, the problem of large and non-uniformgrain size of the LiFePO₄ powders may also occur.

In addition, LiFePO₄, LiMnPO₄, LiNiPO₄ and LiCoPO₄ has olivine structureand similar theoretical specific capacities. But the theoretical voltageplateaus are different. For example, the voltage plateau of LiFePO₄ is3.4V, the voltage plateau of LiMnPO₄ is 4.1V, the voltage plateau ofLiCoPO₄ is 4.8V, and the voltage plateau of LiNiPO₄ is 5.6V. AlthoughLiMnPO₄, LiNiPO₄ and LiCoPO₄ has higher theoretical mass-energy densitythan LiFePO₄, the conductivity of LiMnPO₄, LiNiPO₄ and LiCoPO₄ is lower,and the ability for transferring lithium ions of LiMnPO₄, LiNiPO₄ andLiCoPO₄ is also poor, resulting in the actual capacitance of thebatteries using LiMnPO₄, LiNiPO₄ and LiCoPO₄ is lower.

Therefore, it is desirable to provide a method for manufacturingmicro-sized, submicron-sized, even nano-sized cathode materials ofLi-ion batteries in a simple way, in order to increase thecharge/discharge efficiency, mass-energy density of the batteries andreduce the cost thereof.

SUMMARY

The object of the present invention is to provide metal (II) phosphatepowders for manufacturing an electrode material (especially, a cathodematerial) of a Li-ion battery and a method for manufacturing the same,wherein the metal (II) phosphate powders have nano, micro, or sub-micrograin size and large length to thickness ratio, and can be applied tothe current process for preparing lithium metal phosphate powders.

Another object of the present invention is to provide lithium metalphosphate powders for Li-ion batteries and a method for manufacturingthe same, wherein the metal (II) phosphate powders of the presentinvention is used to manufacture the lithium metal phosphate powders.Hence, the thermal-annealed powders have uniform and small grain size innano, micro, or sub-micro scale, so the grinding process and the sievingprocess can be omitted. Additionally, the obtained lithium metalphosphate powders have large length to thickness ratio, which canimprove the charge/discharge efficiency of the Li-ion batteries.

To achieve the object, the method for manufacturing metal (II) phosphatepowders of the present invention comprises the following steps: (A)providing a P-containing precursor solution, wherein the P-containingprecursor solution comprises: a P-containing precursor, and a weaklyalkaline compound; and (B) adding at least one metal (II) compound intothe P-containing precursor solution to obtain metal (II) phosphatepowders.

In addition, the present invention also provides metal (II) phosphatepowders, which are prepared through the aforementioned method, to applyto prepare electrode materials for Li-ion batteries. The metal (II)phosphate powders for manufacturing the electrode materials of Li-ion ofthe present invention are represented by the following formula (I):(Fe_(1-x)M_(x))₃(PO₄)₂ .yH₂O  (I)wherein M comprises at least one metal selected from the groupconsisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag,Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<x≤1, y is aninteger of 0 to 8, the metal phosphate (II) powders are composed ofplural flake powders, and the length of each of the flake powders isranged from 50 nm to 10 μm.

In addition, the present invention also provides a method formanufacturing lithium metal phosphate powders for a Li-ion battery,wherein the aforementioned metal (II) phosphate powders are used asFe-containing precursors. The method for manufacturing lithium metalphosphate powders of the present invention comprises the followingsteps: (a) providing the aforementioned metal (II) phosphate powders;(b) mixing the metal (II) phosphate powders with a Li-containingprecursor to obtain mixed powders; and (c) heat-treating the mixedpowders to obtain lithium metal phosphate powders.

When the aforementioned method for manufacturing lithium metal phosphatepowders of the present invention is applied, the obtained lithium metalphosphate powders of the present invention are represented by thefollowing formula (II):LiFe_(1-a)M_(a)PO₄  (II)wherein M comprises at least one metal selected from the groupconsisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag,Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<a≤1, the lithiummetal phosphate powders are composed of plural flake powders, and thelength of each of the flake powders is ranged from 50 nm to 10 μm.

The metal (II) phosphate powders for manufacturing electrode materialsof Li-ion batteries of the present invention have uniform and smallgrain size in nano, micro, or sub-micro scale, and especially largelength to thickness ratio. However, the grain size of the conventionalmetal (II) phosphate powders or the conventional ferrous phosphateprecursors is large and non-uniform, so the thermal-annealing process(i.e. the heat-treating process) has to be performed for at least tenhours, in order to completely transform the metal (II) phosphate powdersor the ferrous phosphate precursors into lithium metal phosphate orlithium iron phosphate. In addition, the grain size of the conventionalthermal-annealed powders is usually large, so a grinding process and asieving process have to be performed to obtain powders with specificsize between 1 μm to 10 μm. However, the metal (II) phosphate powders ofthe present invention have uniform and small size, large length tothickness ratio, and specific shapes. Hence, the metal (II) phosphatepowders can be completely transformed into lithium metal phosphatewithin several hours (less than 10 hours), so the time for thethermal-annealing process can be greatly reduced. In addition, theobtained lithium metal phosphate powders still have the similar size andthe similar shape as those of the metal (II) phosphate powders after thethermal-annealing process, so the electrode materials of the Li-ionbatteries can be obtained without performing the grinding process andthe sieving process. Hence, when the metal (II) phosphate powders of thepresent invention are used to prepare lithium metal phosphate powders,the time for the thermal-annealing process can be reduced, and thegrinding process and the sieving process can be omitted. Therefore, thecost for manufacturing the Li-ion batteries can be further reduced. Inaddition, the metal (II) phosphate powders of the present invention canbe directly applied to the current production lines of lithium metalphosphate powders, so it is unnecessary to build new production linesfor manufacturing lithium metal phosphate powders by use of the metal(II) phosphate powders of the present invention. Therefore, the cost formanufacturing the Li-ion batteries can be further reduced.

In the metal (II) phosphate powders or the lithium metal phosphatepowders of the present invention, the flake powders are powders composedof independent flakes, flake powders that one end of each of the flakepowders connects to each other, flake powders connecting to each otherat the center of the flakes, or flake powders that one end of each ofthe flake powders connects to each other to form a connecting center. Inone embodiment of the present invention, the flake powders areindependent flakes. In another embodiment of the present invention, theflake powders connect to each other to form a connecting center.

Furthermore, in the metal (II) phosphate powders or the lithium metalphosphate powders of the present invention, the length of each of theflake powder may be ranged from 50 nm to 10 μm. For example, the lengthof each of the flake powder may be 50 nm˜10 μm, 50 nm˜5 μm, 50 nm˜3 μm,50 nm˜2 μm, 50 nm˜1 μm, 50 nm˜900 nm, 50 nm˜800 nm, 50 nm˜700 nm, 50nm˜600 nm, 50 nm˜500 nm, 50 nm˜400 nm, 50 nm˜300 nm, 100 nm˜10 μm, 100nm˜5 μm, 100 nm˜3 μm, 100 nm˜2 μm, 100 nm˜1 μm, 100 nm˜900 nm, 100nm˜800 nm, 100 nm˜700 nm, 100 nm˜600 nm, 100 nm˜500 nm, 100 nm˜400 nm,100 nm˜300 nm, 200 nm˜10 μm, 200 nm˜5 μm, 200 nm˜3 μm, 200 nm˜2 μm, 200nm˜1 μm, 200 nm˜900 nm, 200 nm˜800 nm, 200 nm˜200 nm, 200 nm˜600 nm, 200nm˜500 nm, 200 nm˜400 nm, 200 nm˜300 nm, 300 nm˜10 μm, 300 nm˜5 μm, 300nm˜3 μm, 300 nm˜2 μm, 300 nm˜1 μm, 300 nm˜900 nm, 300 nm˜800 nm, 300nm˜700 nm, 300 nm˜600 nm, 300 nm˜500 nm, 300 nm˜400 nm, 400 nm˜10 μm,400 nm˜5 μm, 400 nm˜3 μm, 400 nm˜2 μm, 400 nm˜1 μm, 400 nm˜900 nm, 400nm˜800 nm, 400 nm˜700 nm, 400 nm˜600 nm, or 400 nm˜500 nm.

In addition, in the metal (II) phosphate powders or the lithium metalphosphate powders of the present invention, the thickness of each of theflake powder may be ranged from 5 nm to 1 μm. For example, the thicknessof each of the flake powder may be 5 nm˜1 μm, 5 nm˜900 nm, 5 nm˜800 nm,5 nm˜700 nm, 5 nm˜600 nm, 5 nm˜500 nm, 5 nm˜400 nm, 5 nm˜300 nm, 5nm˜200 nm, 5 nm˜150 nm, 5 nm˜140 nm, 5 nm˜130 nm, 5 nm˜120 nm, 5 nm˜110nm, 5 nm˜100 nm, 5 nm˜90 nm, 5 nm˜80 nm, 5 nm˜70 nm, 5 nm˜60 nm, 5 nm˜50nm, 5 nm˜40 nm, 5 nm˜30 nm, 5 nm˜25 nm, 5 nm˜20 nm, 5 nm˜15 nm, 5 nm˜10nm, 10 nm˜1 μm, 10 nm˜900 nm, 10 nm˜800 nm, 10 nm˜700 nm, 10 nm˜600 nm,10 nm˜500 nm, 10 nm˜400 nm, 10 nm˜300 nm, 10 nm˜200 nm, 10 nm˜150 nm, 10nm˜140 nm, 10 nm˜130 nm, 10 nm˜120 nm, 10 nm˜110 nm, 10 nm˜100 nm, 10nm˜90 nm, 10 nm˜80 nm, 10 nm˜70 nm, 10 nm˜60 nm, 10 nm˜50 nm, 10 nm˜40nm, 10 nm˜30 nm, 10 nm˜25 nm, 10 nm˜20 nm, 10 nm˜15 nm, 15 nm˜1 μm, 15nm˜900 nm, 15 nm˜800 nm, 15 nm˜700 nm, 15 nm˜600 nm, 15 nm˜500 nm, 15nm˜400 nm, 15 nm˜300 nm, 15 nm˜200 nm, 15 nm˜150 nm, 15 nm˜140 nm, 15nm˜130 nm, 15 nm˜120 nm, 15 nm˜110 nm, 15 nm˜100 nm, 15 nm˜90 nm, 15nm˜80 nm, 15 nm˜70 nm, 15 nm˜60 nm, 15 nm˜50 nm, 15 nm˜40 nm, 15 nm˜30nm, 15 nm˜25 nm, 15 nm˜20 nm, 20 nm˜1 μm, 20 nm˜900 nm, 20 nm˜800 nm, 20nm˜700 nm, 20 nm˜600 nm, 20 nm˜500 nm, 20 nm˜400 nm, 20 nm˜300 nm, 20nm˜200 nm, 20 nm˜150 nm, 20 nm˜140 nm, 20 nm˜130 nm, 20 nm˜120 nm, 20nm˜110 nm, 20 nm˜100 nm, 20 nm˜90 nm, 20 nm˜80 nm, 20 nm˜70 nm, 20 nm˜60nm, 20 nm˜50 nm, 20 nm˜40 nm, 20 nm˜30 nm, 30 nm˜1 μm, 30 nm˜900 nm, 30nm˜800 nm, 30 nm˜700 nm, 30 nm˜600 nm, 30 nm˜500 nm, 30 nm˜400 nm, 30nm˜300 nm, 30 nm˜200 nm, 30 nm˜150 nm, 30 nm˜140 nm, 30 nm˜130 nm, 30nm˜120 nm, 30 nm˜110 nm, 30 nm˜100 nm, 30 nm˜90 nm, 30 nm˜80 nm, 30nm˜70 nm, 30 nm˜60 nm, 30 nm˜50 nm, 30 nm˜40 nm, 40 nm˜1 μm, 40 nm˜900nm, 40 nm˜800 nm, 40 nm˜700 nm, 40 nm˜600 nm, 40 nm˜500 nm, 40 nm˜400nm, 40 nm˜300 nm, 40 nm˜200 nm, 40 nm˜150 nm, 40 nm˜140 nm, 40 nm˜130nm, 40 nm˜120 nm, 40 nm˜110 nm, 40 nm˜100 nm, 40 nm˜90 nm, 40 nm˜80 nm,40 nm˜70 nm, 40 nm˜60 nm, or 40 nm˜50 nm.

Moreover, in the metal (II) phosphate powders or the lithium metalphosphate powders of the present invention, the ratio of the length andthe thickness of each of the flake powder may be in a range from 10 to500. For example, the ratio of the length and the thickness of each ofthe flake powder may be 10˜500, 10˜400, 10˜300, 10˜200, 10˜150, 10˜130,10˜100, 10˜90, 10˜80, 10˜70, 10˜60, 10˜50, 10˜40, 10˜30, 10˜20, 10˜15,20˜500, 20˜400, 20˜300, 20˜200, 20˜150, 20˜130, 20˜100, 20˜90, 20˜80,20˜70, 20˜60, 20˜50, 20˜40, 20˜30, 30˜500, 30˜400, 30˜300, 30˜200,30˜150, 30˜130, 30˜100, 30˜90, 30˜80, 30˜70, 30˜60, 30˜50, 30˜40,40˜500, 40˜400, 40˜300, 40˜200, 40˜150, 40˜130, 40˜100, 40˜90, 40˜80,40˜70, 40˜60, 40˜50, 50˜500, 50˜400, 50˜300, 50˜200, 50˜150, 50˜130,50˜100, 50˜90, 50˜80, 50˜70, or 50˜60.

Since the thickness of the metal (II) phosphate powders is innano-scale, the thermal-annealing time for preparing the lithium metalphosphate powders can be greatly reduced and the grinding process and asieving process can further be omitted. In addition, since the thicknessof the lithium metal phosphate powders is also in nano-scale, thecharge/discharge efficiency of the obtained Li-ion batteries can furtherbe improved.

Furthermore, the metal (II) phosphate powders of the present inventionare crystallized metal (II) phosphate powders, which may have acrystallization degree of more than 10%.

In the method for manufacturing metal (II) phosphate powders of thepresent invention, the metal (II) compound can be any metal saltcontaining Fe, Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd,Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and/or Nb. Preferably, themetal (II) compound is a sulfate, a carbonate, a nitrate, an oxalate, anacetate, a chlorite, a bromide, or an iodide of Fe, Mn, Co, Ni, Cu, Cr,V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg,Ca, Sr, B or Nb. More preferably, the metal (II) compound is a sulfate,a carbonate, a nitrate, an oxalate, an acetate, a chlorite, a bromide,or an iodide of Fe, Mn, Co, Cu, Ni, Zn, or Mg. Hence, in one embodimentof the present invention, the M in the formula (I) can comprise at leastone metal selected from the group consisting of Mn, Co, Cu, Ni, Zn, andMg. In another embodiment of the present invention, the M in the formula(II) can comprise at least one metal selected from the group consistingof Mn, Co, Cu, Ni, Zn, and Mg.

In one embodiment of the present invention, the M in the formula (I) canbe Mn, Co, Ni or Cu, and 0.6≤x≤1. In another embodiment of the presentinvention, the metal (II) phosphate powders may be represented by thefollowing formula (I-1):(Fe_(1-x1-x2)Mn_(x1)M′_(x2))₃(PO₄)₂ .yH₂O  (I-1)wherein M′ comprises at least one metal selected from the groupconsisting of Co, Cu, Ni, Zn, and Mg, 0.2≤x1≤0.8, 0.05≤x2≤0.4,0.5<x1+x2≤1, and y is an integer of 0 to 8.

In one embodiment of the present invention, the M in the formula (II)can be Mn, Co, Ni or Cu, and 0.6≤a≤1. In another embodiment of thepresent invention, when M in the formula (II) is Mn, 0.5<a<1. Forexample, 0.5<a<0.99, 0.6≤a<1, or 0.6≤a<0.99. In another embodiment ofthe present invention, the lithium metal phosphate powders may berepresented by the following formula (II-1):LiFe_(1-a1-a2)Mn_(a1)M′_(a2)PO₄  (II-1)wherein M′ comprises at least one metal selected from the groupconsisting of Co, Cu, Ni, Zn, and Mg, 0.2≤a1≤0.8, 0.05≤a2≤0.4, and0.5<a1+a2≤1.

The method for manufacturing metal (II) phosphate powders of the presentinvention may further comprise a step (c) after the step (b): washingthe metal (II) phosphate powders. Herein, the metal (II) phosphatepowders can be washed with ethanol, water, or a combination thereof.Preferably, the metal (II) phosphate powders are washed with deionizedwater. In addition, the method for manufacturing metal (II) phosphatepowders of the present invention may further comprise a step (d) afterthe step (c): drying the obtained metal (II) phosphate powders. As thetemperature of the drying process is increased, the time thereof can bereduced. Preferably, the metal (II) phosphate powders are dried at40-120° C. for 10-120 hours. More preferably, the metal (II) phosphatepowders are dried at 50-70° C. for 10-120 hours.

In the lithium metal phosphate powders of the present invention, thelithium metal phosphate powders of the present invention have olivinestructures. In one embodiment of the present invention, the X-raydiffraction pattern of the obtained lithium metal phosphate powders canbe consistent with the standard lithium metal phosphate. In anotherembodiment of the present invention, at least one peak in the X-raydiffraction pattern of the obtained lithium metal phosphate powders canbe a little bit shifted compared with the standard lithium metalphosphate.

In one embodiment of the present invention, the X-ray diffractionpattern of the obtained metal (II) phosphate powders can be consistentwith the standard metal (II) phosphate. In another embodiment of thepresent invention, at least one peak in the X-ray diffraction pattern ofthe obtained metal (II) phosphate powders can be a little bit shiftedcompared with the standard metal (II) phosphate.

Furthermore, in the methods for manufacturing the metal (II) phosphatepowders, the P-containing precursor can be at least one selected fromthe group consisting of H₃PO₄, NaH₂PO₄, Na₂HPO₄, Mg₃(PO₄)₂, andNH₄H₂PO₄. Preferably, the P-containing precursor is H₃PO₄, NH₄H₂PO₄, ora combination thereof.

In addition, in the methods for manufacturing the metal (II) phosphatepowders of the present invention, the weakly alkaline compound may be atleast one selected from the group consisting of Na₂CO₃, and NaHCO₃.Preferably, the weakly alkaline compound is NaHCO₃.

In the methods for manufacturing the lithium metal phosphate powders ofthe present invention, the Li-containing precursor may be at least oneselected from the group consisting of LiOH, Li₂CO₃, LiNO₃, CH₃COOLi,Li₂C₂O₄, Li₂SO₄, LiCl, LiBr, LiI, LiH₂PO₄, Li₂HPO₄, and Li₃PO₄.Preferably, the Li-containing precursor is LiOH, Li₂SO₄, LiH₂PO₄, orLi₃PO₄. More preferably, the Li-containing precursor is Li₃PO₄.

In addition, in the methods for manufacturing the lithium metalphosphate powders of the present invention, the metal (II) phosphatepowders are mixed with the Li-containing precursor and at least onecarbon-containing material to obtain the mixed powders in step (b). Inthis case, the surfaces of the obtained lithium metal phosphate powdersare coated with carbon, so the conductivity of the obtained lithiummetal phosphate powders can further be increased. In addition, thecarbon-containing material can also inhibit the growth of the lithiummetal phosphate powders, so the size of the lithium metal phosphatepowders can be kept small. Herein, the carbon-containing material can beany sugar such as sucrose, stearic acid, citric acid, lauric acid,polystyrene, polystyrene ball (PS ball), graphene oxide, glucose, andalso be vitamin C (L-ascorbate). In addition, the additional amount ofthe carbon-containing material can be 0.1-40 wt % of the weight of theobtained lithium metal phosphate powders. Preferably, the additionalamount of the carbon-containing material is 2.5-30 wt % of the weight ofthe obtained lithium metal phosphate powders.

In the methods for manufacturing the lithium metal phosphate powders ofthe present invention, one or more types of the metal (II) phosphatepowders can be used in the step (b). In one embodiment of the presentinvention, if lithium metal phosphate powders containing one metal isdesired, one type of the metal (II) phosphate powders can be used in thestep (b). In another embodiment of the present invention, if lithiummetal phosphate powders containing two metals is desired, one type ofthe metal (II) phosphate powders containing two metals can be used inthe step (b), or one type of the metal (II) phosphate powders containingone metal and another type of the metal (II) phosphate powderscontaining another metal can be used together in the step (b). However,the present disclosure is not limited thereto, and the use of the metal(II) phosphate powders can be adjusted according to the metals containedin the desired lithium metal phosphate powders.

In the methods for manufacturing the lithium metal phosphate powders ofthe present invention, the mixed powders can be heat-treated under anatmosphere or vacuum or with an introduced gas flow to obtain thelithium metal phosphate powders, in step (c). In one aspect, the mixedpowders can be heat-treated under an introduced gas flow to obtain thelithium metal phosphate powders, and the pressure of the introduced gasflow was around 1 atm. In another aspect, a vacuum is created in theheat-treating tube, followed by introducing gas into the heat-treatingtube, and then the heat-treating tube is sealed to undergo theheat-treating process to obtain the lithium metal phosphate powders,wherein the pressure in the heat-treating tube has to be keep less than1 atm during the heat-treating process. In further another aspect, avacuum is created in the heat-treating tube and sealed withoutintroducing any gas, followed by undergoing the heat-treating procedureto obtain the lithium metal phosphate powders. Herein, the atmosphere orthe introduced gas flow can be used as a protection gas or a reductiongas, which may comprise at least one selected from the group consistingof N₂, H₂, He, Ne, Ar, Kr, Xe, CO, methane, Ar—H₂ mixed gas, N₂—H₂ mixedgas, and a mixture thereof. Preferably, the protection gas or thereduction gas is N₂, H₂, Ar, Ar—H₂ or N₂—H₂ mixed gas. More preferably,the protection gas or the reduction gas is N₂—H₂ or Ar—H₂ mixed gas.

Furthermore, in the methods for manufacturing the lithium metalphosphate powders of the present invention, the mixed powders areheat-treated at 300-900° C., preferably. In addition, the mixed powdersare preferably heat-treated for 1-20 hours. More preferably, the mixedpowders are heat-treated at 500-860° C. for 2-10 hours.

The obtained lithium metal phosphate powders of the present inventioncan be used as electrode materials (for example, cathode materials) toprepare Li-ion batteries, through any conventional method in the art.Here, the method for manufacturing the Li-ion batteries is simplydescribed, but the present invention is not limited thereto.

An anode and a cathode are provided. Herein, the anode can be a Li-plateor an anode made by a carbon material, which is prepared by coating ananode current collector with a carbon material, and then drying andpressing the carbon material to form an anode for the Li-ion battery.The cathode current collector is coated with a cathode active material(i.e. the lithium metal phosphate powders of the present invention), andthen the cathode active material is dried and pressed to form a cathodefor the Li-ion battery. Next, a separator is inserted between thecathode and the anode, a Li-containing electrolyte is injected, and thena Li-ion battery is obtained after an assembling process.

Other objects, advantages, and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a SEM photo of Mn₃(PO₄)₂ prepared in Example 14 of the presentinvention.

FIG. 2 is a SEM photo of Co₃(PO₄)₂ prepared in Example 16 of the presentinvention.

FIG. 3 is a SEM photo of Cu₃(PO₄)₂ prepared in Example 17 of the presentinvention.

FIG. 4 is a SEM photo of (Mn_(0.8)Fe_(0.1)Mg_(0.1))₃(PO₄)₂ prepared inExample 3 of the present invention.

FIG. 5 is a SEM photo of (Mn_(0.8)Fe_(0.1)Co_(0.1))₃(PO₄)₂ prepared inExample 1 of the present invention.

FIG. 6 is a SEM photo of (Mn_(0.8)Fe_(0.1)Zn_(0.1))₃(PO₄)₂ prepared inExample 2 of the present invention.

FIG. 7 is a SEM photo of (Mn_(0.8)Fe_(0.1)Ni_(0.1))₃(PO₄)₂ prepared inExample 4 of the present invention.

FIG. 8 is a SEM photo of (Mn_(0.6)Fe_(0.2)Ni_(0.2))₃(PO₄)₂ prepared inExample 5 of the present invention.

FIG. 9 is a SEM photo of (Mn_(0.55)Fe_(0.3)Ni_(0.15))₃(PO₄)₂ prepared inExample 6 of the present invention.

FIG. 10 is a SEM photo of (Fe_(0.4)Mn_(0.2)Ni_(0.2)Mg_(0.2))₃(PO₄)₂prepared in Example 11 of the present invention.

FIG. 11 is a SEM photo of LiMnPO₄ prepared in Example 26 of the presentinvention.

FIG. 12 is a SEM photo of LiMnPO₄ prepared in Example 27 of the presentinvention.

FIG. 13 is a SEM photo of LiCoPO₄ prepared in Example 28 of the presentinvention.

FIG. 14 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 18of the present invention.

FIG. 15 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 19of the present invention.

FIG. 16 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 20of the present invention.

FIG. 17 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 21of the present invention.

FIG. 18 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 22of the present invention.

FIG. 19 is a SEM photo of LiFe_(0.4)Mn_(0.55)Ni_(0.05)PO₄ prepared inExample 23 of the present invention.

FIG. 20 is a TEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 20of the present invention.

FIG. 21 is a perspective view showing a Li-ion battery according to thepresent invention.

FIG. 22 shows the relation between the voltage and the specificcapacities of a Li-ion battery prepared with lithium metal phosphatepowders according to Example 19 of the present invention.

FIG. 23 shows the relation between the voltage and the specificcapacities of a Li-ion battery prepared with lithium metal phosphatepowders according to Example 19 of the present invention.

FIG. 24 shows the relation between the voltage and the specificcapacities of a Li-ion battery prepared with lithium metal phosphatepowders according to Example 20 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention has been described in an illustrative manner, andit is to be understood that the terminology used is intended to be inthe nature of description rather than of limitation. Many modificationsand variations of the present invention are possible in light of theabove teachings. Therefore, it is to be understood that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

Analysis

The shapes of the metal (II) phosphate powders and the lithium metalphosphate powders obtained in the following examples (Ex) were observedwith a scanning electron microscope (SEM) (Hitachi S-4000).

In addition, the metal (II) phosphate powders and the lithium metalphosphate powders obtained in the following examples were also examinedwith an X-ray diffractometer (Shimadzu 6000) to understand the crystalstructure thereof. The X-ray diffraction pattern was collected by Cu Kαradiation, the 2θ-scanning angle is 15°-45°, and the scanning rate is1°/min. The standards for X-ray examination are listed in the followingTable 1.

TABLE 1 Compound Standard Mn₃(PO₄)₂•3H₂O JCPDS No. 3-426 Mn₃(PO₄)₂•7H₂OJCPDS No. 84-1160 Ni₃(PO₄)₂•8H₂O JCPDS No. 46-1388 or JCPDS No. 1-126Co₃(PO₄)₂•8H₂O JCPDS No. 33-432 Cu₃(PO₄)₂•3H₂O JCPDS No. 22-548Fe₃(PO₄)₂•8H₂O JCPDS No. 79-1928 LiMnPO₄ JCPDS No. 33-804 LiCoPO₄ JCPDSNo. 85-2 LiFePO₄ JCPDS No. 81-1173Preparation of Metal (II) Phosphate PowdersStep I

H₃PO₄ and NaHCO₃ were added into 500 ml of de-ionized water in a molarratio of 1:3 to obtain a P-containing precursor solution, and theP-containing precursor solution was stirred for 30 min.

Step II

To prepare Mn₃(PO₄)₂, MnSO₄.5H₂O was added into the obtainedP-containing precursor solution, wherein a molar ratio of MnSO₄.5H₂O toH₃PO₄ was 3:2.

To prepare (Fe_(1-x)Mn_(x))₃(PO₄)₂, MnSO₄.5H₂O and FeSO₄.7H₂O were addedinto the obtained P-containing precursor solution, wherein a molar ratioof a total amount of MnSO₄.5H₂O and FeSO₄.7H₂O to H₃PO₄ was 3:2, and amolar ratio of MnSO₄.5H₂O to FeSO₄.7H₂O was adjusted on the basis of thedesired (Fe_(1-x)Mn_(x))₃(PO₄)₂ shown in the following Table 2.

To prepare Fe₃(PO₄)₂, FeSO₄.7H₂O was added into the obtainedP-containing precursor solution, wherein a molar ratio of FeSO₄.7H₂O toH₃PO₄ was 3:2.

To prepare metal (II) phosphate powders containing two or more metalsselected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn,Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B andNb, two or more suitable metal (II) sulfates were used, wherein a molarratio of a total amount of the used metal (II) sulfates to H₃PO₄ was3:2, and a molar ratio between the used metal (II) sulfates are adjustedon the basis of the desired metal (II) phosphate powders shown in thefollowing Table 2.

Step III

The obtained products in Step II were washed with de-ionized water andthen collected with centrifugation for three times.

Step IV

The collected products in Step III were dried at 55° C. for 12 to 108hr, and metal (II) phosphate powders shown in the following Table 2 wereobtained.

The shapes of the metal (II) phosphate powders were observed by SEM, andthe obtained were also examined with an X-ray diffractometer. Theresults are listed in the following Table 2.

TABLE 2 Ex Compound Color Shape XRD summary 1(Mn_(0.8)Fe_(0.1)Co_(0.1))₃(PO₄)₂ Light Thickness: 10~15 nm Peakssimilar to brown Length: 50~900 nm Mn₃(PO₄)₂•3H₂O, Irregular independentbut right-shifting flakes 2 (Mn_(0.8)Fe_(0.1)Zn_(0.1))₃(PO₄)₂ MilkyThickness: 20~80 nm Peaks similar to yellow Plates with flakesMn₃(PO₄)₂•3H₂O, attached on their but right-shifting surface Length(plates): 1~3 μm Length (flakes): 60~150 nm Irregular plates andgathered flakes 3 (Mn_(0.8)Fe_(0.1)Mg_(0.1))₃(PO₄)₂ Milky Thickness:10~15 nm Peaks similar to yellow Length: 300~900 nm Mn₃(PO₄)₂•3H₂O,Irregular independent but right-shifting flakes 4(Mn_(0.8)Fe_(0.1)Ni_(0.1))₃(PO₄)₂ Milky Thickness: 10~15 nm Peakssimilar to yellow Length: 200~800 nm Mn₃(PO₄)₂•3H₂O, Irregularindependent but right-shifting flakes 5(Mn_(0.6)Fe_(0.2)Ni_(0.2))₃(PO₄)₂ Chartreuse Thickness: 60~100 nm Peakssimilar to Length: 1~3 μm Fe₃(PO₄)₂•8H₂O Plates 6(Mn_(0.55)Fe_(0.3)Ni_(0.15))₃(PO₄)₂ Cyan Thickenss: 20~100 nm Peakssimilar to Length: 1~3 μm Fe₃(PO₄)₂•8H₂O Plates 7(Mn_(0.6)Fe_(0.3)Ni_(0.10))₃(PO₄)₂ Cyan Thickenss: 80~130 nm Peakssimilar to Length: 1~3 μm Fe₃(PO₄)₂•8H₂O Plates 8(Mn_(0.55)Fe_(0.4)Ni_(0.05))₃(PO₄)₂ Camel Thickness: 50~140 nm Peakssimilar to green Length: 1~3 μm Fe₃(PO₄)₂•8H₂O Plates 9(Mn_(0.575)Fe_(0.4)Ni_(0.025))₃(PO₄)₂ Yellow tan Thickness: 10~15 nmPeaks similar to Length: 300 nm~1 μm Fe₃(PO₄)₂•8H₂O, Irregularindependent but poor flakes crystallinity 10(Fe_(0.4)Mn_(0.2)Ni_(0.2)Mg_(0.2))₃(PO₄)₂ Blue Thickness: 10 nm Peakssimilar to Length: 50~300 nm Fe₃(PO₄)₂•8H₂O, Cloudy flakes butright-shifting 11 (Fe_(0.4)Mn_(0.2)Ni_(0.2)Mg_(0.2))₃(PO₄)₂ BlueThickness: 50~100 nm Peaks similar to Plates with flakes Fe₃(PO₄)₂•8H₂O,attached on their but right-shifting surface Length (plates): 1~2 μmLength (flakes): 50~200 nm Irregular plates and flakes 12(Mn_(0.6)Fe_(0.4))₃(PO₄)₂ Khaki Thickness: 10~15 nm Most peaks areLength: 300~900 nm consistent to Irregular flakes peaks ofMn₃(PO₄)₇•7H₂O and Fe₃(PO₄)₂•8H₂O, and 3 peaks cannot be identified. 13(Mn_(0.9)Fe_(0.1))₃(PO₄)₂ Light Thickness: 10 nm Major peaks are yellowLength: 100~600 nm consistent to the Irregular independent peaks offlakes Mn₃(PO₄)₂•3H₂O, but some peaks are consistent to the peaks ofMn₃(PO₄)₂•7H₂O. 14 Mn₃(PO₄)₂ Light pink Thicknesss: 10~15 nm Major peaksare Length: 300~900 nm consistent to the Irregular independent peaks offlakes Mn₃(PO₄)₂•3H₂O, but some peaks are consistent to the peaks ofMn₃(PO₄)₂•7H₂O after drying for 108 hr. 15 Ni₃(PO₄)₂ Apple Thickness: 10nm Peaks similar to green Length: 100~300 nm Ni₃(PO₄)₂•8H₂O Circularflakes 16 Co₃(PO₄)₂ Pink The thickness is Peaks similar to purple variedaccording to Co₃(PO₄)₂•8H₂O, the reaction time. but right-shiftingThickness: 15 min: 90~700 nm 60 s: 20~300 nm 45 s: 10~40 nm Length: 15min: 3~10 μm 60 s: 400 nm~1 μm 45 s: 400 nm~1 μm One end of each of theflake powders connects to each other to form a connecting center. 17Cu₃(PO₄)₂ Baby blue Thickness: 10~15 nm Peaks similar to Length: 200~500nm Cu₃(PO₄)₂•3H₂O Flakes formed into a 3D net shape

FIG. 1 is a SEM photo of Mn₃(PO₄)₂ prepared in Example 14 of the presentinvention. FIG. 2 is a SEM photo of Co₃(PO₄)₂ prepared in Example 16 ofthe present invention. FIG. 3 is a SEM photo of Cu₃(PO₄)₂ prepared inExample 17 of the present invention. FIG. 4 is a SEM photo of(Mn_(0.8)Fe_(0.1)Mg_(0.1))₃(PO₄)₂ prepared in Example 3 of the presentinvention. FIG. 5 is a SEM photo of (Mn_(0.8)Fe_(0.1)Co_(0.1))₃(PO₄)₂prepared in Example 1 of the present invention. FIG. 6 is a SEM photo of(Mn_(0.8)Fe_(0.1)Zn_(0.1))₃(PO₄)₂ prepared in Example 2 of the presentinvention. FIG. 7 is a SEM photo of (Mn_(0.8)Fe_(0.1)Ni_(0.1))₃(PO₄)₂prepared in Example 4 of the present invention. FIG. 8 is a SEM photo of(Mn_(0.6)Fe_(u)Ni_(0.2))₃(PO₄)₂ prepared in Example 5 of the presentinvention. FIG. 9 is a SEM photo of (Mn_(0.55)Fe_(0.3)Ni_(0.1))₃(PO₄)₂prepared in Example 6 of the present invention. FIG. 10 is a SEM photoof (Fe_(0.4)Mn_(0.2)Ni_(0.2)Mg_(0.2))₃(PO₄)₂ prepared in Example 11 ofthe present invention. From FIG. 1 to FIG. 10, it can be found that mostof the observed metal (II) phosphates have flake shapes with thinthicknesses and long lengths.

In addition, the rate for adding MnSO₄.5H₂O into the P-containingprecursor solution relates to the formation of Mn₃(PO₄)₂.3H₂O andMn₃(PO₄)₂.7H₂O. When MnSO₄.5H₂O is added rapidly, more Mn₃(PO₄)₂.3H₂O isobtained. When MnSO₄.5H₂O is added slowly, more Mn₃(PO₄)₂.7H₂O isobtained. Furthermore, even though the collected products in Step IIIwere dried at 55° C. for 12 to 108 hr, the water molecules inMn₃(PO₄)₂.7H₂O cannot be removed completely. Thus, for preparing lithiummetal phosphate powders, the thermal gravimetric analysis (TGA) is heldto calculate the content of the water molecular in the manganese (II)phosphate.

Similarly, for other metal (II) phosphate with different crystalscontaining different amount of water molecules, TGA is also held tocalculate the content of the water molecular in the metal (II)phosphate.

Furthermore, the rate for adding metal (II) sulfates into theP-containing precursor solution is also related to the thickness of theobtained metal (II) phosphate.

Preparation of Lithium Metal Phosphate Powders

Step A: Ball Milling Process

A-1: Preparation by One Metal (II) Phosphate Powder and Li₃PO₄

One metal (II) phosphate powder was used as a precursor, and mixed withLi₃PO₄ in a molar ratio of 1:1. In addition, 15 wt % of sugar or 6.5 wt% of polystyrene was also added in the mixture. The mixture was mixedwith a 3D shaker containing 0.8 mm zirconia balls for 2 hr to obtainmixed powders.

A-2: Preparation by Two or More Metal (II) Phosphate Powder and Li₃PO₄

Two or more metal (II) phosphate powders was used as precursors, andmixed with Li₃PO₄, wherein a molar ratio of a total amount of the metal(II) phosphate powders to Li₃PO₄ was 1:1. In addition, 15 wt % of sugaror 6.5 wt % of polystyrene (PS) was also added in the mixture. Themixture was mixed with a 3D shaker containing 0.8 mm zirconia balls for2 hr to obtain mixed powders.

In one example, 1 wt % of graphene oxide was also added as a carbonsource into the mixture.

Step B: Heat Treating Process

The product obtained in Step A was thermal-annealed at 750° C., under aN₂ gas flow (1 atm) for 3 hr. Finally, lithium metal phosphate powderscoated with carbon and formed in flake shapes were obtained.

Alternatively, a vacuum is created in the heat-treating tube, followedby introducing N₂ gas into the heat-treating tube, and then theheat-treating tube is sealed. The product obtained in Step A wasthermal-annealed at 750° C. in the sealed heat-treating tube under N₂atmosphere for 3 hr. The pressure was kept under 1 atm during theheat-treating process. Finally, lithium metal phosphate powders coatedwith carbon and formed in flake shapes were obtained.

The shapes of the obtained lithium metal phosphate powders were observedby SEM, and the obtained were also examined with an X-raydiffractometer. The results are listed in the following Table 3.

TABLE 3 Step Carbon XRD Ex Compound Precursor A source Shape Summary 18LiFe_(0.4)Mn_(0.6)PO₄ Mn₃(PO₄)₂ A-2 Sugar Thickness: Peaks Fe₃(PO₄)₂10~15 nm consistent to Length: LiFePO₄ when 300~900 nm 2θ < 35°Irregular Peaks locating independent between flakes LiFePO₄ and LiMnPO₄when 2θ > 35° 19 LiFe_(0.4)Mn_(0.6)PO₄ Mn₃(PO₄)₂ A-2 PS Thickness: PeaksFe₃(PO₄)₂ 10~15 nm consistent to Length: LiFePO₄ when 300~900 nm 2θ <35° Irregular Peaks locating independent between flakes (95%) LiFePO₄and and bulk LiMnPO₄ powders (5%) when 2θ > 35° 20 LiFe_(0.4)Mn_(0.6)PO₄Mn₃(PO₄)₂ A-2 Sugar Thickness: Peaks Fe₃(PO₄)₂ Graphene 10~15 nmconsistent to oxide Length: LiFePO₄ when 300~900 nm 2θ < 35° IrregularPeaks locating independent between flakes (more LiFePO₄ and gathered)LiMnPO₄ when 2θ > 35° 21 LiFe_(0.4)Mn_(0.6)PO₄ (Mn_(0.6)Fe_(0.4))₃ A-1Sugar Thickness: Most peaks (PO₄)₂ 10 nm consistent with Length:LiFePO₄, and 300~900 nm some peaks (70%) shifted 70~150 nm (30%) Flakeswith rounding edges 22 LiFe_(0.4)Mn_(0.6)PO₄ (Mn_(0.6)Fe_(0.4))₃ A-1 PSThickness: Most peaks (PO₄)₂ 10 nm consistent with Circular flakes,LiFePO₄, and Length: some peaks 300~700 nm shifted (50%) Irregularflakes, Length: 300~700 nm (25%) Irregular broken flakes, Length: <100nm (10%) Big circular flakes, Length: around 2.5 μm (15%) 23LiFe_(0.4)Mn_(0.55) (Mn_(0.55)Fe_(0.4) A-1 Sugar Thickness: PeaksNi_(0.05)PO₄ Ni_(0.05))₃(PO₄)₂ 20 nm consistent to Circular flakes,LiFePO₄ Length: 250~900 nm Irregular flakes with rounding edges, Length:60~500 nm 24 LiFe_(0.2)Mn_(0.8)PO₄ Mn₃(PO₄)₂ A-2 Sugar Thickness: PeaksFe₃(PO₄)₂ 10~15 nm consistent to Length: LiFePO₄ when 300~900 nm 2θ <21° Independent Peaks locating flakes between LiFePO₄ and LiMnPO₄ when2θ > 21° 25 LiFe_(0.4)Mn_(0.55) Mn₃(PO₄)₂ A-2 Sugar Thickness: PeaksCo_(0.05)PO₄ Fe₃(PO₄)₂ 10~15 nm consistent to Co₃(PO₄)₂ Length: LiFePO₄when 300~900 nm 2θ < 35° Independent Peaks locating flakes betweenLiFePO₄ and LiMnPO₄ when 2θ > 35° 26 LiMnPO₄ Mn₃(PO₄)₂ A-1 SugarThickness: Peaks 10 nm consistent to Length: LiMnPO₄ 300~900 nmIndependent flakes 27 LiMnPO₄ Mn₃(PO₄)₂ A-1 PS Thickness: Peaks 10 nmconsistent to Length: LiMnPO₄ 500 nm~2 μm Independent flakes 28 LiCoPO₄Co₃(PO₄)₂ A-1 Sugar Thickness: Peaks 10~20 nm consistent to Length:LiCoPO₄ 300 nm~1.5 μm Independent flakes 29 LiMn_(0.6)Co_(0.4)PO₄Mn₃(PO₄)₂ A-2 Sugar Thickness: Peaks Co₃(PO₄)₂ 10~20 nm consistent toLength: LiCoPO₄ when 300~900 nm 2θ < 27° Flakes with Peaks locatingrounding edges between LiCoPO₄ and LiMnPO₄ when 2θ > 27°

FIG. 11 is a SEM photo of LiMnPO₄ prepared in Example 26 of the presentinvention. FIG. 12 is a SEM photo of LiMnPO₄ prepared in Example 27 ofthe present invention. FIG. 13 is a SEM photo of LiCoPO₄ prepared inExample 28 of the present invention. FIG. 14 is a SEM photo ofLiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 18 of the present invention.FIG. 15 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 19of the present invention. FIG. 16 is a SEM photo ofLiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 20 of the present invention.FIG. 17 is a SEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 21of the present invention. FIG. 18 is a SEM photo ofLiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 22 of the present invention.FIG. 19 is a SEM photo of LiFe_(0.4)Mn_(0.55)Ni_(0.05)PO₄ prepared inExample 23 of the present invention. From FIG. 11 to FIG. 19, it can befound that the observed lithium metal phosphates have flake shapes withthin thicknesses and long lengths.

FIG. 20 is a TEM photo of LiFe_(0.4)Mn_(0.6)PO₄ prepared in Example 20of the present invention. From the result shown in FIG. 20, it can befound reduced graphene oxide is present between flakes, and the flakesare coated with a uniform carbon film.

According to the results of Examples 1 to 17, the meal (II) phosphatepowders have small and uniform grain size. When these metal (II)phosphate powders are used as a precursor for preparing lithium ionphosphate powders, the time for the heat-treating process can beshortened. Hence, the cost for manufacturing the Li-ion batteries can befurther reduced. In addition, the thermal-annealed lithium metalphosphate powders have similar shape to that of metal (II) phosphatepowders, so the thermal-annealed lithium metal phosphate powders alsohave small and uniform grain size. Hence, the grinding process and thesieving process can be omitted during the process for preparing thecathode materials, so the cost of Li-ion batteries can be reduced.Furthermore, according to the results of Examples 18 to 29, the lithiummetal phosphate powders of the present invention have nano, micro, orsub-micro grain size. When the lithium metal phosphate powders of thepresent invention are used as cathode materials of Li-ion batteries, theLi-ion batteries can exhibit uniform charging and discharging current,and excellent charge/discharge efficiency. Hence, not only the cost ofthe Li-ion batteries can be reduced, but also the charge/discharge timecan be shortened and the capacity of the batteries can be furtherimproved.

Preparation and Testing of Li-Ion Batteries

The Li-ion battery of the present invention was prepared through theconventional manufacturing method thereof. Briefly, PVDF, lithium metalphosphate powders of Examples 19 and 20, ZrO, KS-6 [TIMCAL] and Super-P[TIMCAL] were dried in a vacuum oven for 24 hr, and a weight ratio oflithium metal phosphate powders:PVDF:KS-6: Super-P was 85:10:3:2. Next,the aforementioned materials were mixed with a 3D miller containing NMPto obtain slurry. An Al foil was provided and coated with the slurrythrough a blade coating process, and then placed in a vacuum oven at 90°C. for 12 hr. The dried foil coated with the slurry was pressed by aroller, and cut into Φ13 mm circular plates.

Next, as shown in FIG. 21, an upper cap 17, a lower cap 11, a wide mouthplate 16, a pad 15, the aforementioned circular plate 12 with the slurrycoated on a surface 121 thereof, and a Φ18 mm separator 13 are placed ina vacuum oven at 90° C. for 24 hr, and then placed into a glove box withless than 1 ppm of water and O₂ under Ar environment. After immersingthe circular plate 12, and the separator 13 with electrolyte, thecircular plate 12, the separator 13, a Li-plate 14, the pad 15, the widemouth plate 16 and the upper cap 17 were sequentially laminated on thelower cap 11, as shown in FIG. 20. After pressing and sealing, a CR2032coin type Li-ion battery was obtained, and tested after 12-30 hr. Theelectrolyte used was 1M LiPF₆ in EC/EMC/DMC (1:1:1 wt %)+1% VC, acommonly used electrolyte for LiFePO₄ battery.

The obtained Li-ion batteries prepared by lithium metal phosphatepowders of Examples 19 and 20 were tested with automatic cellcharge-discharge test system (AcuTech Systems BAT-750B). FIG. 22 showthe relations between the voltage and the specific capacities of aLi-ion battery prepared with lithium metal phosphate powders accordingto Example 19 of the present invention, wherein the lithium metalphosphate powders is prepared by a heat treatment process under sealedN₂ atmosphere. FIG. 23 show the relations between the voltage and thespecific capacities of a Li-ion battery prepared with lithium metalphosphate powders according to Example 19 of the present invention,wherein the lithium metal phosphate powders is prepared by a heattreatment process under a N₂ gas flow. FIG. 24 show the relationsbetween the voltage and the specific capacities of a Li-ion batteryprepared with lithium metal phosphate powders according to Example 20 ofthe present invention, wherein the lithium metal phosphate powders isprepared by a heat treatment process under a N₂ gas flow.

FIG. 22 to FIG. 24 show the relations between the voltage and thespecific capacities of a Li-ion battery prepared with lithium metalphosphate powders according to Examples 19 and 20 of the presentinvention, which was tested by the same charge and discharge current(0.1 C, 0.2 C, 0.5 C, 0.75 C and 1 C) at 30-40 cycles. From the resultsshown in FIG. 22 and FIG. 23, it can be found that the specificcapacities of the batteries thereof under 0.1 C discharge current wasabout 152 mAh/g, and was less than that of the batteries prepared withlithium metal phosphate powders of example 20 which is above 160 mAh/gas shown in FIG. 24. An average discharging voltage of about 3.6 V wasobtained for batteries prepared with lithium metal phosphate powders ofexample 19 which was higher than the values 3.2-3.4 V of the batteriesprepared with LiFePO₄. These results indicate the energy density of theLi-ion battery prepared with lithium metal phosphate powders accordingto Example 19 would be higher than that of the LiFePO₄ battery, althougha commonly used low voltage electrolyte for LiFePO₄ battery was applied.

In conclusion, the metal (II) phosphate powders of the present inventionhave thin thickness, and high length to thickness ratio. Hence, the timefor preparing lithium metal phosphate powders can be greatly reduced. Inaddition, when the obtained lithium metal phosphate powders are furtherapplied to prepare Li-ion batteries, the performance of the batteriescan be greatly improved.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the invention as hereinafter claimed.

What is claimed is:
 1. Lithium metal phosphate powders for a Li-ionbattery, represented by the following formula (II):LiFe_(1-a)M_(a)PO₄  (II) wherein M comprises at least one metal selectedfrom the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc,Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb,0.5<a≤1, the lithium metal phosphate powders are composed of pluralflake powders, and a length of each of the flake powders is ranged from50 nm to 10 μm.
 2. The lithium metal phosphate powders of claim 1,wherein the flake powders are powders composed of independent flakes,flake powders that one end of each of the flake powders connects to eachother, flake powders connecting to each other at the center of theflakes, or flake powders that one end of each of the flake powdersconnects to each other to form a connecting center.
 3. The lithium metalphosphate powders of claim 1, wherein M comprises at least one metalselected from the group consisting of Mn, Co, Cu, Ni, Zn, and Mg.
 4. Thelithium metal phosphate powders of claim 1, wherein a thickness of eachof the flake powders is ranged from 5 nm to 1 μm.
 5. The lithium metalphosphate powders of claim 1, wherein M is Mn, Co, Ni or Cu, and0.6≤a≤1.
 6. The lithium metal phosphate powders of claim 1, representedby the following formula (II-1):LiFe_(1-a1-a2)Mn_(a1)M′_(a2)PO₄  (II-1) wherein M′ comprises at leastone metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg,0.2≤a1≤0.8, 0.05≤a2≤0.4, and 0.5<a1+a2≤1.
 7. A method for manufacturinglithium metal phosphate powders, comprising the following steps: (a)providing metal (II) phosphate powders represented by the followingformula (I):(Fe_(1-x)M_(x))₃(PO₄)₂ .yH₂O  (I) wherein M comprises at least one metalselected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn,Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B andNb, 0.5<x≤1, y is an integer of 0 to 8, the metal phosphate (II) powdersare composed of plural flake powders, and a length of each of the flakepowders is ranged from 50 nm to 10 μm; (b) mixing the metal (II)phosphate powders with a Li-containing precursor to obtain mixedpowders; and (c) heat-treating the mixed powders to obtain lithium metalphosphate powders represented by the following formula (II):LiFe_(1-a)M_(a)PO₄  (II) wherein M comprises at least one metal selectedfrom the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc,Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb,0.5<a≤1, the lithium metal phosphate powders are composed of pluralflake powders, and a length of each of the flake powders is ranged from50 nm to 10 μm.
 8. The method of claim 7, wherein the step (a) comprisesthe following steps: (a1) providing a P-containing precursor solution,wherein the P-containing precursor solution comprises: a P-containingprecursor, and a weakly alkaline compound; and (a2) adding at least onemetal (II) compound into the P-containing precursor solution to obtainthe metal (II) phosphate powders represented by the formula (I).
 9. Themethod of claim 8, wherein the P-containing precursor is at least oneselected from the group consisting of H₃PO₄, NaH₂PO₄, Na₂HPO₄,Mg₃(PO₄)₂, and NH₄H₂PO₄.
 10. The method of claim 8, wherein the weaklyalkaline compound is at least one selected from the group consisting ofNa₂CO₃, and NaHCO₃.
 11. The method of claim 8, wherein the metal (II)compound is a sulfate, a carbonate, a nitrate, an oxalate, an acetate, achlorite, a bromide, or an iodide of Fe, Mn, Co, Ni, Cu, Cr, V, Mo, Ti,Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B orNb.
 12. The method of claim 7, wherein the Li-containing precursor is atleast one selected from the group consisting of LiOH, Li₂CO₃, LiNO₃,CH₃COOLi, Li₂C₂O₄, Li₂SO₄, LiCl, LiBr, LiI, LiH₂PO₄, Li₂HPO₄, andLi₃PO₄.
 13. The method of claim 7, wherein the metal (II) phosphatepowders are mixed with the Li-containing precursor and at least onecarbon-containing material to obtain the mixed powders in the step (b).14. The method of claim 13, wherein the carbon-containing material issugar, stearic acid, citric acid, lauric acid, polystyrene, polystyreneball (PS ball), graphene oxide, glucose, or vitamin C.
 15. The method ofclaim 7, wherein the mixed powders is heat-treated under an atmosphereor vacuum or with an introduced gas flow to obtain the lithium metalphosphate powders, in the step (c).
 16. The method of claim 15, whereinthe atmosphere or the introduced gas flow comprises at least oneselected from the group consisting of N₂, H₂, He, Ne, Ar, Kr, Xe, CO,methane, Ar—H₂ mixed gas, and N₂—H₂ mixed gas.
 17. The method of claim7, wherein the lithium metal phosphate powders are represented by thefollowing formula (II-1):LiFe_(1-a1-a2)Mn_(a1)M′_(a2)PO₄  (II-1) wherein M′ comprises at leastone metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg,0.2≤a1≤0.8, 0.05≤a2≤0.4, and 0.5<a1+a2≤1.
 18. The method of claim 7,wherein the flake powders are powders composed of independent flakes,flake powders that one end of each of the flake powders connects to eachother, flake powders connecting to each other at the center of theflakes, or flake powders that one end of each of the flake powdersconnects to each other to form a connecting center.